In certain known types of photographic shutters, one or more light obstructing elements, such as blades or curtain members, move initially to an open position to admit light through the exposure opening, followed shortly thereafter by movement of one or more other light obstructing elements, such as blades or curtains, from an open position to a closed position, to terminate the exposure. This is particularly true in shutters of the so-called focal plane type, although occasionally two sets of elements are encountered in shutters of the objective type as distinguished from the focal plane type. The present invention deals particularly with the timing of the interval between commencement of movement of the first element (or group of elements) which may be called the opening or leading element, and the commencement of movement of the second element (or group of elements) which may be called the closing or trailing element. The present invention is particularly suitable for use in shutters of the focal plane type although some features of the invention may be useful also in shutters of the objective type, since the invention relates basically to the timing of the exposure interval, rather than to any details of construction of the opening or leading element and the closing or trailing element, which details may be conventional and are unimportant so far as the present invention is concerned.
As well understood in the art, the light obstructing means which moves to open the exposure aperture of the camera may be a single element or a group or set of two or more elements, which merely for convenience may be referred to in the singular as an element, intending thereby to include the plural. Likewise the other or trailing light obstructing means, initially open and moved to terminate the exposure, may similarly be constructed as a single element or a plurality of elements, and again the singular expression element is intended to include the plural. Each element may also be referred to as an blade or a curtain. The time interval between the commencement of movement of the opening or leading element and the commencement of movement of the closing or trailing element determines the length or duration of the exposure, and also determines the width of the so-called slit in the case of a focal plane shutter. It is the control mechanism for determining this time interval which forms the subject matter of the present invention. As already indicated, details of construction of the light obstructing elements or blades themselves, and other details of the camera, are not important for purposes of the present invention and may be widely varied within the skill of the art.
The present invention deals particularly with timing mechanism of mechanical construction for timing the start of the closing movement of the second light obstructing element, with relation to the time of start of opening movement of the first light obstructing element.
An object of the invention is the provision of a simplified and improved form of mechanical timing mechanism (as distinguished from the electrical or electronic timing mechanism) which will operate smoothly, efficiently, and reliably without causing undesirable jolts or vibrations.
Another object is the provision so designed that it is relatively compact and space-saving, requiring little room in the camera.
Still another object is the provision of such mechanical timing mechanism in a form suitable for use in a camera having provision for timing the shutter both mechanically and electronically, the mechanical timing mechanism being so constructed that it may be rendered inoperative in an easy manner, when it is desired to set the camera for electronic timing rather than mechanical timing.